The invention relates to an apparatus for measuring the imbalance of rotors, such as motor vehicle wheels, and more particularly to an apparatus for relieving the potential effects of stress associated with excessively high torque when such measuring apparatus is started.
In conventional imbalance measuring apparatus the rotor to be balanced is secured to a primary shaft by a clamping device having a tensioning nut of the kind in which the drive torque transmitted from an electric motor to the primary shaft is transmitted by means of friction to the rotor to be measured. Such tensioning nuts may lessen when the electric motor is switched on because of high torque applied to the primary shaft at that time. Since clamping devices of this kind are conventionally used for centering the rotor on the primary shaft, the loosening of these rotor clamps is important.